Ink-jet printing is a non-impact printing process in which droplets of ink are deposited on a print medium in a particular order to form alphanumeric characters, area-fills, and other patterns thereon. An ink-jet image is formed when a precise pattern of dots is ejected from a drop-generating device, known as a "printhead", onto a printing medium. The typical inkjet printhead has an array of precisely formed nozzles in an orifice plate typically comprised of a planar substrate comprised of a polymer material and attached to a thermal ink-jet printhead substrate. The substrate incorporates an array of firing chambers that receive liquid ink (colorants dissolved or dispersed in a solvent) from a supply channel (or ink feed channel) leading from one or more ink reservoirs. Each chamber has a thin film resistor, known as a "firing resistor, " located opposite the nozzle. A barrier layer located between the substrate and the orifice forms the boundaries of the firing chamber and provides fluidic isolation from neighboring firing chambers. The printhead is mounted on and protected by an outer packaging referred to as a print cartridge.
The thin film substrate is typically comprised of a substrate such as silicon on which are formed various thin film layers that form thin film ink firing resistors, apparatus for enabling the resistors, and also interconnections to bonding pads that are provided for external electrical connections to the printhead. The thin film substrate more particularly includes a top thin film layer of tantalum disposed over the resistors as a thermomechanical passivation layer.
The ink barrier layer is typically a polymer material that is laminated as a dry film to the thin film substrate, and is designed to be photo-definable and both UV and thermally curable.
When the resistor is heated, a thin layer of ink above the resistor is vaporized to create a drive bubble. This forces an ink droplet out through the nozzle. After the droplet leaves and the bubble collapses, capillary force draws ink from the ink feed channel to refill the nozzle.
Typically, as the printhead scans across the print medium, the ink and other unwanted debris may accumulate on the orifice plate. To minimize the presence of this unwanted material, the printhead is wiped clean by a wiper material (typically on-board the printer) typically made of EPDM rubber. The wiping, among other things, may lead to a change in the surface morphology of the orifice plate around the nozzle due to creep and flow of the orifice plate material. This change, herein referred to as "ruffles, " in the orifice plate, may in turn lead to misdirected ink drops, hence print quality defects.
Thus, it would be advantageous to provide an improved ink-jet printhead with improved orifice plate to minimize unwanted print defects.